A Novel Ferroceneylazobenzene Self-Assembled Monolayer on an ITO Electrode: Photochemical and Electrochemical Behaviors

Abstract

A novel ferroceneylazobenzene self-assembled monolayer (SAM) has been constructed on an indium-tin oxide (ITO) electrode via the covalent attachment of 4-(4'-11-ferrocenyl-undecanoxyphenylazo)benzoic acid ( FcAzCOOH) onto a silanized ITO substrate surface and verified by reflectance infrared spectroscopy and water contact angle. Atomic force microscopy (AFM) and cyclic voltammogram (CV) indicated that the FcAzCOOH formed a uniform and reproducible SAM on the ITO electrode with a surface coverage of ca. 1.9 x 10 (-10) mol/cm (2) (87 A (2)/molecule). The reversible photoisomerization behavior of the SAM was characterized by UV-vis spectra. The azo pi-pi* transition band intensity of the SAM gradually decreased with UV (365 nm) irradiation and was almost recovered again when subsequent exposure to ambient room light (400-800 nm). The increased tilt angle of the molecules on the ITO substrate after UV irradiation further confirmed the trans-to- cis isomerization of azobenzene moieties. The CV of the trans- FcAzCOOH modified ITO electrode showed a pair of waves due to redox of the ferrocene groups in the potential range of 0 to +800 mV (vs SCE), and the peak separation of the redox wave became larger after UV irradiation and almost returned to its original value after subsequent exposure to the visible light. Rate-dependent CV curves indicated that the charge transfer rate between the ferrocene species in the SAM and the ITO electrode was slowed down after UV irradiation due to the smaller porosity of the monolayer film and the more compact barrier layer between the redox species and the ITO electrode. It is the first time to directly observe the influence of photoisomerization of the azobenzene moiety on the redox behavior of redox species in the ferroceneylazobenzene-functionalized SAM. The present results provide profound insight into the role of redox microenvironment on electron transfer kinetics and also provide a simple and facile approach to the preparation of photocontrollable electrodes.

Amination of surfaces via self-assembly of dopamine

“…Ferrocene functionalized gold electrode (Fc/DA/Au) was prepared by the following method [11]. The DA/Au (dopamine monolayer-modified Au substrate) substrate was pretreated as mentioned above and used immediately for the next step.…”

“…Ferrocene-terminated, self-assembled monolayers (Fc-SAMs) have been widely studied as an electrochemically active surface on electrode [10][11][12]49]. Herein, we also use the formation of the convenient, robust, and well-reproducible ferrocene-terminated SAMs to testify and apply the existence of as-prepared dopamine monolayer on Au substrate; as a result, we realize the attachment of ferrocene dopamine SAMs through the amidation reaction of NHS-activated Fc with amino groups of dopamine monolayer.…”

“…In recent years, forming SAMs on different surfaces, such as metallic, semiconductive, plastic substrates, so as to alter the interface properties, has attracted considerable attentions for biological/chemical sensing, molecule-based electronic devices, catalysis, photovoltaic devices, wetting control, and so on [2][3][4][5][6][7][8][9][10][11][12]. Generally, the molecules for forming SAMs have ''headgroups'' that adsorb or chemically bind onto substrates to form well-defined organic surfaces with alterable chemical functionalities at the other end being exposed to environment.…”

EGaIn Microelectrode for Electrical Characterization of ITO-Based van der Waals Interface and Airborne Molecular Contamination of ITO Surface

“…26 The surface OH groups provide reactive sites at which further chemistry can occur to functionalize the surface. [26][27][28][29][30] Despite the extensive use of ITO thin film-based electrodes in a variety of optoelectronic devices, little is known about the role of the ITO surface-cleaning process in the electrical performance of the ITO electrodes-particularly, the electrical transport through the ITO-based vdW interface. This work addresses the following issues: i) how adventitious molecular contamination by airborne contaminants on the surface of an ITO thin film affects the electrical behavior of the ITO-based vdW interface; and ii) the ability of UV and/or ozone treatments, and organic-solvent (EtOH) rinsing to improve the electrical performance of ITO electrodes in large-area junctions.…”

Synthesis and photochemical properties of cationic cyclopentadienyliron containing arylazo chromophores

“…Some complexes can reversibly isomerize by light irradiation [8][9][10]. Reversible trans-cis photo-isomerization of azo chromophores may be used to design and exploit novel photoactive materials [11][12][13].…”